Conventionally, as a representative one of extracorporeal circulation devices, a cardiopulmonary assist device used for a cardiopulmonary assist is known. Such a device is provided with a blood extracorporeal circulation circuit composed of an oxygenator, centrifugal artificial heart (centrifugal pump), controller, oxygen supply source (oxygen tank), and so forth (see, e.g., Japanese patent 4839030).
The cardiopulmonary assist device functions in place of the heart and lung of a patient and is required to have high safety so that it may be prevented from falling into a situation in which it stops in an operation.
One method for ensuring the safety is providing a controller for controlling the respective units configuring the circulation circuit with a duplicated structure with main controller and sub-controller. This is because the sub-controller continues control even if the main controller stops due to any cause. To determine whether or not the main controller is in the stop state, the sub-controller transmits a signal to the main controller at adequate timing and makes the determination based on whether or not a response signal thereof can be received from the main controller. That is, the sub-controller determines that the main controller is in the stop state if the response signal cannot be received within a predetermined time.
As described above, doubling the controller allows construction of a safer system. However, on the other hand, there is a problem that the circuit scale becomes more complicated and increases in the device size and the power consumption are caused.
Furthermore, particularly in the case of artificial heart and lung, during an operation, it is important that the blood flows with an amount of fluid matching the amount per unit time as commanded by a doctor or a person performing the operation. Therefore, even if the main controller issues an erroneous control signal to a drive unit for the centrifugal pump due to any cause, this has not been detected by the prior art as an abnormality.